Reset properly errno before calling write()

6cb3372 enforces errno to ENOSPC when less bytes than what is expected
have been written when it is unset, though it forgot to properly reset
errno before doing a system call to write(), causing errno to
potentially come from a previous system call.

Reported-by: Tom Lane
Author: Michael Paquier
Reviewed-by: Tom Lane
Discussion: https://postgr.es/m/31797.1533326676@sss.pgh.pa.us

7 files changed, 14 insertions, 0 deletions

diff --git a/src/backend/access/heap/rewriteheap.c b/src/backend/access/heap/rewriteheap.c
index ed7ba181c79..85f92973c95 100644
--- a/src/backend/access/heap/rewriteheap.c
+++ b/src/backend/access/heap/rewriteheap.c
@@ -1166,6 +1166,7 @@ heap_xlog_logical_rewrite(XLogReaderState *r)
 	len = xlrec->num_mappings * sizeof(LogicalRewriteMappingData);
 
 	/* write out tail end of mapping file (again) */
+	errno = 0;
 	pgstat_report_wait_start(WAIT_EVENT_LOGICAL_REWRITE_MAPPING_WRITE);
 	if (write(fd, data, len) != len)
 	{
diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index e8d4e37fe30..ed3e36c0c2a 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -1665,6 +1665,7 @@ RecreateTwoPhaseFile(TransactionId xid, void *content, int len)
 						path)));
 
 	/* Write content and CRC */
+	errno = 0;
 	pgstat_report_wait_start(WAIT_EVENT_TWOPHASE_FILE_WRITE);
 	if (write(fd, content, len) != len)
 	{
diff --git a/src/backend/replication/logical/origin.c b/src/backend/replication/logical/origin.c
index 595eb252d2a..46156ae6c6f 100644
--- a/src/backend/replication/logical/origin.c
+++ b/src/backend/replication/logical/origin.c
@@ -576,6 +576,7 @@ CheckPointReplicationOrigin(void)
 						tmppath)));
 
 	/* write magic */
+	errno = 0;
 	if ((write(tmpfd, &magic, sizeof(magic))) != sizeof(magic))
 	{
 		int			save_errno = errno;
@@ -619,6 +620,7 @@ CheckPointReplicationOrigin(void)
 		/* make sure we only write out a commit that's persistent */
 		XLogFlush(local_lsn);
 
+		errno = 0;
 		if ((write(tmpfd, &disk_state, sizeof(disk_state))) !=
 			sizeof(disk_state))
 		{
@@ -641,6 +643,7 @@ CheckPointReplicationOrigin(void)
 
 	/* write out the CRC */
 	FIN_CRC32C(crc);
+	errno = 0;
 	if ((write(tmpfd, &crc, sizeof(crc))) != sizeof(crc))
 	{
 		int			save_errno = errno;
diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c
index 9b55b94227b..1d43a165ad0 100644
--- a/src/backend/replication/logical/reorderbuffer.c
+++ b/src/backend/replication/logical/reorderbuffer.c
@@ -2421,6 +2421,7 @@ ReorderBufferSerializeChange(ReorderBuffer *rb, ReorderBufferTXN *txn,
 
 	ondisk->size = sz;
 
+	errno = 0;
 	pgstat_report_wait_start(WAIT_EVENT_REORDER_BUFFER_WRITE);
 	if (write(fd, rb->outbuf, ondisk->size) != ondisk->size)
 	{
diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
index e975faeb8c9..ea454181946 100644
--- a/src/backend/replication/logical/snapbuild.c
+++ b/src/backend/replication/logical/snapbuild.c
@@ -1609,6 +1609,7 @@ SnapBuildSerialize(SnapBuild *builder, XLogRecPtr lsn)
 		ereport(ERROR,
 				(errmsg("could not open file \"%s\": %m", path)));
 
+	errno = 0;
 	pgstat_report_wait_start(WAIT_EVENT_SNAPBUILD_WRITE);
 	if ((write(fd, ondisk, needed_length)) != needed_length)
 	{
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index fb95b44ed82..94f7a99cfa4 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -1275,6 +1275,7 @@ SaveSlotToPath(ReplicationSlot *slot, const char *dir, int elevel)
 				SnapBuildOnDiskChecksummedSize);
 	FIN_CRC32C(cp.checksum);
 
+	errno = 0;
 	pgstat_report_wait_start(WAIT_EVENT_REPLICATION_SLOT_WRITE);
 	if ((write(fd, &cp, sizeof(cp))) != sizeof(cp))
 	{
diff --git a/src/bin/pg_basebackup/walmethods.c b/src/bin/pg_basebackup/walmethods.c
index fbfee05a5a6..42e3f3023a0 100644
--- a/src/bin/pg_basebackup/walmethods.c
+++ b/src/bin/pg_basebackup/walmethods.c
@@ -122,6 +122,7 @@ dir_open_for_write(const char *pathname, const char *temp_suffix, size_t pad_to_
 		zerobuf = pg_malloc0(XLOG_BLCKSZ);
 		for (bytes = 0; bytes < pad_to_size; bytes += XLOG_BLCKSZ)
 		{
+			errno = 0;
 			if (write(fd, zerobuf, XLOG_BLCKSZ) != XLOG_BLCKSZ)
 			{
 				int			save_errno = errno;
@@ -445,6 +446,7 @@ tar_write_compressed_data(void *buf, size_t count, bool flush)
 		{
 			size_t		len = ZLIB_OUT_SIZE - tar_data->zp->avail_out;
 
+			errno = 0;
 			if (write(tar_data->fd, tar_data->zlibOut, len) != len)
 			{
 				/*
@@ -629,6 +631,7 @@ tar_open_for_write(const char *pathname, const char *temp_suffix, size_t pad_to_
 
 	if (!tar_data->compression)
 	{
+		errno = 0;
 		if (write(tar_data->fd, tar_data->currentfile->header, 512) != 512)
 		{
 			save_errno = errno;
@@ -829,6 +832,7 @@ tar_close(Walfile f, WalCloseMethod method)
 		return -1;
 	if (!tar_data->compression)
 	{
+		errno = 0;
 		if (write(tar_data->fd, tf->header, 512) != 512)
 		{
 			/* if write didn't set errno, assume problem is no disk space */
@@ -901,6 +905,7 @@ tar_finish(void)
 	MemSet(zerobuf, 0, sizeof(zerobuf));
 	if (!tar_data->compression)
 	{
+		errno = 0;
 		if (write(tar_data->fd, zerobuf, sizeof(zerobuf)) != sizeof(zerobuf))
 		{
 			/* if write didn't set errno, assume problem is no disk space */
@@ -933,6 +938,7 @@ tar_finish(void)
 			{
 				size_t		len = ZLIB_OUT_SIZE - tar_data->zp->avail_out;
 
+				errno = 0;
 				if (write(tar_data->fd, tar_data->zlibOut, len) != len)
 				{
 					/*